Application of Cuscuta japonica Powder as a Low-Cost Biosorbent for the Removal of Atrazine and Diuron from Aqueous Solution: Kinetic, Isothermal, and Thermodynamic Studies

Abstract

The extensive use of herbicides such as atrazine and diuron has caused contamination of water sources posing a significant risk to the environment and human. Several methods have been employed in the removal of herbicides from water with adsorption offering a viable and a promising solution due to its relative low cost and environmental friendliness. In this study, the efficacy of Cuscuta japonica powder in removing atrazine and diuron from water was evaluated. Cuscuta japonica powder prepared from Cuscuta japonica vines and characterized using Fourier Transform Infrared Spectroscopy, Scanning Electron Microscopy, Energy-dispersive X-ray Spectroscopy and Thermogravimetric analysis. Adsorption kinetics of the two herbicides was studied by varying the reaction time while maintaining all other conditions constant. The isothermal studies were done by carrying the adsorption studies at different initial concentrations while the thermodynamic studies were done by monitoring the adsorption process at different temperatures. The herbicides were prepared shortly before use. All the studies were carried in triplicates and blanks were used. Cuscuta japonica powder achieved a maximum percent removal of 85.23 and 79% for atrazine and diuron, respectively. The adsorption capacity of Cuscuta japonica powder for atrazine and diuron were 54.73 and 39.87 mg/g, respectively. The removal efficiency of the two herbicides from water decreased with increase in the molar mass of the herbicides. The adsorption process of atrazine and diuron onto Cuscuta japonica powder followed the Elovich kinetic model, recording R² values of 0.937 and 0.946, respectively, signifying a chemical adsorption process. The adsorption of the two herbicides best fitted the Langmuir isotherm model, with R² values of 0.983 for atrazine and 0.992 for diuron. The thermodynamic results showed that the adsorption process for the two herbicides onto the Cuscuta japonica powder was feasible, spontaneous, and exothermic as shown by negative values for ∆G and ∆H. The negative ∆S values obtained indicate increased order at the sorbent/solution interface during adsorption. This is the first report on the potential of Cuscuta japonica derived adsorbent in removal of pollutants from water. In conclusion, the invasive Cuscuta japonica has a potential application as an adsorbent for the removal of pollutants from water. This may serve as a cost effective way of eliminating this problematic plant.